New Views of Lunar Pits

When the Sun is well overhead, the floor of the Mare Tranquillitatis pit is illuminated. With an incidence angle of 26.5° and a shadow of 55 meters, scientists can estimate the depth to be a bit over 100 meters.

Spectacular high Sun view of the Mare Tranquillitatis pit crater revealing boulders on an otherwise smooth floor. Image is 400 meters wide, north is up. Credit: NASA/GSFC/Arizona State University

That estimate is from the edge of the shadow, which begins a slightly downslope from the gradual margin of the pits. When measured from the level of the surrounding mare plain, the depth of the pit is even greater. Compare this depth to the width, which ranges from 100 to 115 meters across the sharp precipice.

Two views of Mare Ingenii pit. Credit: NASA/GSFC/Arizona State University

A pair of Mare Ingenii pit images (each panel is 150 meters wide) reveals different portions of the floor as the Sun crosses from West to East (Left M123485893RE, Right M128202846LE). Shadow measurements indicate that the Ingenii pit is about 70 meters deep and its width is about 120 meters. The Sun angle, direction, and elevation perfectly illuminate the layered nature of the mare basalts. Each shelf corresponds to a local lava flow event. By climbing down this “staircase” a geologist astronaut can sample increasingly further back in time.

Variations in lighting reveal the structure of the fascinating lunar pit craters. The center panel, with the Sun high above, gives scientists a great view of the Maurius Hills pit floor. Each panel is 300 meters wide. Credit: NASA/GSFC/Arizona State University

LROC has now imaged the Marius Hills pit three times, each time with very different lighting. The center view has an incidence angle of 25° that illuminates about three-quarters of the floor. The Marius pit is about 34 meters deep and 65 by 90 meters wide. Read more about the Ingenii, Tranquillitatis, and Marius pits. Do any of these pits provide access to still-open/uncollapsed lava tubes? What could be learned by visiting and exploring one or all of these fascinating features? Imagine entering a preserved lava tube, unchanged for more than 3 billion years; such an opportunity is a geologist’s paradise – a chance to travel back in time to see what brand-new lava flows look like! What types of rare minerals might exist on these hidden surfaces (if they exist)? Do you think we should send a robot into one of the pits? How about astronauts; is it worth sending humans in to explore? How would you like to explore this amazing feature?

First, they should get some low incidence angle photos of these pits, see if we can see along the tube at all or determine whether there is any overhang inside.

If it does look like it is a running lava tube, there should be a robotic lander that can anchor into the surface, with a little camera on a tether. Drop the camera over the edge... take some nice high res panoramic shots. Maybe include a high power flash and map all the visible crevices.

That would be so awesome if there was a whole network of caves on the moon... There might even be ice in there, right?

The problem would be having the light be just right for the shot, otherwise all you will get is a picture of a dark pit.

Ice is unlikely in those tubes/caves. They most likely formed, drained, and solidified from magma early. While still out gassing, they would have been to hot for water vapor to freeze. But anything is possible.